1. Field of the Invention
The invention relates to portable automobile security alarms, and more particularly to a window mounted alarm having a siren mounted externally to the window.
2. Description of the Prior Art
Automobile theft is a pervasive problem. In the past, various types of automobile protection systems have been devised to protect automobiles from theft. Such alarm systems are secured to the automobile frame or chassis and move with the car upon a tampering attempt. Such systems contain motion sensors operative to detect tampering or movement of the automobile to trigger an alarm. The alarms can be acoustic alarms designed to announce intrusions, deter further intrusions, and attract help from passers by. Such systems are generally powered by the car battery.
Automobile alarm systems have been connected with the automobile car horn to generate the acoustic alarm. These systems are permanently installed in the vehicle and require a considerable amount of time and labor thus being far from portable. Such systems require some degree of skill to mount on an automobile and are expensive to manufacture and install. Because such systems are electronically sophisticated they are often prone to malfunction.
New and used cars on sales lots are an open invitation to thieves and vandals. It is impractical to install a permanent alarm system on a car that may only be on the lot for a few days. Thus, portable and detachable alarm systems are useful for businesses with a great turnover of automobiles, such as automobile dealerships. They can be easily removed and replaced as cars are sold. Portable alarms are easily mounted, inexpensive to make and purchase, and give the user the option of utilizing the device on multiple vehicles. Generally, a siren within the alarm unit is used instead of the horn. Because of their portable nature, the capacity of the power source is limited.
Disturbance sensitive portable automobile alarm devices have been designed to hang over the top edge of a side window of an automobile with compartment like structures on both sides. The devices can utilize a motion sensor and an internal power source within the interior compartment and can generate an audible alarm and/or transmit a radio frequency ("RF") signal upon activation. Indicator lights on the device provide an indication of active status. Examples of such devices can be found in U.S. Pat. Nos. 4,155,067 to Gleeson and 4,187,497 to Howell et al. While serving their intended purpose of sounding an alarm such devices suffer the shortcoming that, for instance, the alarm of Gleeson is in two separable and easily disconnectable parts and the alarm of Howell et al. fails to afford propagation of the audible alarm at a sufficiently high intensity to ensure a reasonably adequate range.
The intensity of an automobile alarm is an important component in its ability to provide an effective deterrent. A shortcoming of smaller portable alarms is that they are often not as loud as permanent alarms that utilize the automobile horn. Their power supply and size limit the intensity of range of the alarm annunciator.